1 3
Topics in Current Chemistry (2020) 378:16
independent catalysts being used to control two different aspects of stereochemistry
within a cooperative process.
While Pd-catalyzed allylic alkylation is well developed, the corresponding enantioselective benzylation reaction is significantly less common. In 2018, Snaddon
OPfp
O
OPfp
O
H
EWG
OTs
Pd(P(2-thienyl) 3 ) 3 (5 mol%)
(R)-BTM (20 mol%)
i Pr 2 NEt (1.1 equiv)
THF, rt
38 Examples
EWG
OPfp
O
H
CO 2 Me
76%
5:1 E:Z
92% ee
Me
OPfp
O
H
CN
79%
9:1 E:Z
76% ee
OPfp
O
H
75%
E Only
90% ee
PhO
N
O
OMe
Me
OPfp
O
H
75%
E Only
94% ee
EtS
O
Br
Selected Examples:
Scheme 22 General catalyst system for asymmetric α-allylation with electron-poor allyl tosylates
88%
94% ee
74%
96% ee
78%
94% ee
43%
88% ee
OPfp
O
N
R 1
OPfp
O
H
N
Me
R 2
OPfp
O
H
N
R 1
OMs
XantphosPdG3 (5 mol%)
(R)-BTM (20 mol%)
THF, rt
9 Examples
OTs
R 2
OPfp
O
H
N
MeO
MeO
OPfp
O
H
N
Me
Me
OPfp
O
H
N
Me
S
Br
OPfp
O
H
N
Me
Cl
OPfp
O
H
N
OMe
O
H
N
89%
96% ee
Selected Examples:
Conversion of allylation product to a 5,7-fused bicycle:
XantphosPdG3 (5 mol%)
(R)-BTM (20 mol%)
THF, rt
14 Examples
1. MeOH, i PrNEt
DMAP, THF, rt
2. Grubbs II, CH 2 Cl 2
40 °C
two steps:
76%, 96% ee
Scheme 23 Asymmetric α-allylation with pyrrole nucleophiles
Reprinted from the journal
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